The EGF receptor (EGFR) is overexpressed in many human tumors implicating it in the pathogenesis of some cancers. To study regulation of the EGFR gene, the promoter region was isolated and shown to contain many transcription factor binding sites including four Sp1 sites and sites for at least three other factors. To isolate transcription factors that bind to the GC-rich region, a labeled GC-rich DNA fragment was used to isolate from an expression library a cDNA that encodes a novel 91 kilodalton protein. When GCF cDNA was attached to a SV40 promoter and cotransfected into CV1 cells with EGF receptor CAT constructions, GCF repressed EGF receptor promoter activity suggesting GCF may be a negative regulatory protein.